Onset of antiferromagnetism inUPt3via Th substitution studied by muon spin spectroscopy

M. J. Graf, A. de Visser, C. P. Opeil, J. C. Cooley, J. L. Smith, A. Amato, C. Baines, F. Gygax, A. Schenck
2003 Physical Review B (Condensed Matter)  
Muon spin spectroscopy has been used to study in detail the onset of large-moment antiferromagnetism (LMAF) in UPt_3 as induced by Th substitution. Zero-field experiments have been carried out on a series of polycrystalline U_1-xTh_xPt_3 (0 <= x <= 0.05) samples in the temperature range 0.04 - 10 K. At low Th content (x <= 0.002) magnetic ordering on the time scale of the uSR experiment (10^-8 s) is not detected. For x = 0.005 a weak magnetic signal appears below T = 2 K, while for 0.006 <= x
more » ... 0.05, spontaneous oscillations in the uSR spectra signal the presence of the LMAF phase. The data are well described by a two-component depolarization function, combining the contribution of a polycrystalline antiferromagnet and a Kubo-Lorentzian response. However, the transition into the antiferromagnetic phase is quite broad. For x = 0.01 and 0.02, a weak magnetic signal appears below about 7 K, which is well above the mean-field transition temperatures. The broadening may be a result of the effects of disorder on the time fluctuations associated with anomalous small-moment antiferromagnetism.
doi:10.1103/physrevb.68.224421 fatcat:ata7zbkj6rhz7blxh22h3jvdsy